U.S. Pat. No. 5,593,711 (Inventor: Pierre Glaesener; Publication Date: 1997 Jan. 14; Assignee: Husky Injection Molding Systems Limited, Canada) discloses a platen for transmitting a clamping force while preventing end face bending by using an intermediate structure distributing forces from the edges of one end face to the centre of the other end face.
U.S. Pat. No. 5,776,402 (Inventor: Pierre Glaesener; Publication Date: 1998 Jul. 7; Assignee: Husky Injection Molding Systems Limited, Canada) discloses a process of distributing forces within a platen by generating force against sidewall(s) in first direction and directing force from one of the sidewalls solely towards the other of the sidewalls.
PCT Patent Number WO 03/084731A1 (Inventor: Wohlrab et al; Publication Date: 2003 Oct. 16; Assignee: Krauss-Maffei Kunststofftechnik GMBH, Germany) discloses a platen for an injection-molding machine. The platen includes a backing frame joined to a front plate by angled ribs that meet the frame outside the tie bar holes.
U.S. Patent Application Number 2004/0208950A1 (Inventor: Pierre Glaesener; Publication Date: 2004 Oct. 21; Assignee: Husky Injection Molding Systems Limited, Canada) discloses a platen for a molding machine. The platen includes a support located between two planar walls having ribs arranged at non-normal angle to a first wall and the rib transmits forces from the first wall to a second wall such that bending of the second wall is resisted.
U.S. Pat. No. 6,439,876 (Inventor: Pierre Glaesener; Publication Date: 2002 Aug. 27; Assignee: Husky Injection Molding Systems Limited, Canada) discloses a mold-support platen that includes spaced-apart ribs interconnecting back face, wall and front face.
PCT Patent Application Number WO 2005/084909 A1 (Inventor: Nagata, Yoshihiko; Publication Date: 15 Sep. 2005; Assignee: Sumitomo Heavy Industries, Japan) discloses a mold support device of a molding system. Apparently, this patent application discloses (with reference to paragraph 0053) that the central parts of four peripheral edges (portions) linked by vertical-border linking members and horizontal-border linking members of mold-mounting part and rear-surface part are separated from tie-bar load-bearing parts. As a result, even if parts in the vicinity of tie-bar load-bearing parts (that is, tie-bar ears) in rear surface should deform as a result of reaction force said tie-bar load-bearing parts receive from tie-bars, said deformation is not transmitted to mold-mounting part, and said mould mounting part does not deform.
FIGS. 1A to 1D are views of molding-system platens 100, 200 in accordance with U.S. Pat. Nos. 5,593,711 and 5,776,402. FIG. 1A is a perspective view of the molding-system platen 100 (hereafter referred to as the “platen” 100) for use in a molding system (not depicted) such as an injection molding system. The platen 100 includes a mold-bearing zone 102 and a force-bearing zone 110. The mold-bearing zone 102 includes a central portion 104 and also includes a peripheral portion 106, and the peripheral portion 106 surrounds the central portion 104. The central portion 104 is coupled to the force-bearing zone 110 while the peripheral portion 106 is decoupled from the force-bearing zone 110. Zone 110 includes tie-bar ears 115 at each corner of the zone 100. The tie-bar ears 115 receive tie bars (not depicted) that transmit a clamping force to the platen 100.
A potential problem with this arrangement is that the tie-bar ears 115 may inadvertently bend or warp responsive to a clamping force being applied to the tie-bar ears 115 via the tie bars (not depicted). However, the tie bar ears 115 may resist deflection if the zone 110 includes a sufficient amount of mass around the tie-bar ears 115 but then this would increase the weight of the platen 100 (and the cost of the platen 100 would increase), and then (if the platen 100 is used as a movable platen) the cycle time of the molding system may increase (which may be not acceptable in some cases). If the platen 100 is used as a movable platen, the issue would be that by inadvertently increasing the weight of the platen 100, the platen 100 would have a larger inertia and therefore the platen 100 would require more time and energy to move in order to keep the cycle time (of the molding system) low.
A mold 160 (depicted in FIG. 1B) is attachable to and detachable from the central portion 104 of the mold-bearing zone 102. The peripheral portion 106 of the mold-bearing zone 102 defines tie-bar passageways 101 that are positioned at the peripherally-located corners of the mold-bearing zone 102. The tie-bar passageways 101 are sized to receive and to permit tie bars 166 (depicted in FIG. 1B) to extend past the mold-bearing zone 102 and toward the force-bearing zone 110. The tie bars 166 are usually coupled to the peripheral corners of the force-bearing zone 110. If the platen 100 is used as a stationary platen, the mold-bearing zone 102 also defines a machine-nozzle passageway 103 sized to permit a molding-system nozzle 164 (depicted in FIG. 1B) to pass through and communicate with a mold cavity 174 (depicted in FIG. 1B) that is defined by the mold 160. If the platen 100 is used as a movable platen, the mold-bearing zone 102 does not define the passageway 103.
A force-transferring structure 162 symmetrically couples the central portion 104 of the mold-bearing zone 102 to the peripheral (upper and lower) edges of the force-bearing zone 110. A force (such as a clamping force and/or a mold-break force) is applied by the tie bars 166 to the peripheral corners of the force-bearing zone 110 and then the force is subsequently symmetrically coupled through the force-transferring structure 162 over to the central portion 104 of the mold-bearing zone 102. In this example, some of the force may be coupled to the peripheral portion 106. In effect, the force is symmetrically focused onto the mold 160 that is attached to the central portion 104. In this manner, the force is more efficiently used in the clamping and mold-break operations associated with the mold 160. The force-transferring structure 162 may be, for example, a hollowed semicircular-shaped body or a quonset-shaped body. While this arrangement focuses the force to the mold 160 (via the central portion 104), it also helps to maintain the mold-bearing zone 102 substantially flat, to prevent bending of the peripheral portion 106 and also to prevent bending of the central portion 104. A benefit of maintaining the mold-bearing zone 102 flat is that the force is applied substantially evenly to the mold 160 so that the mold 160 does not become exposed to unevenly applied forces. In effect, the mold 160 is prevented from becoming worn down by unevenly-applied forces, and so this arrangement may extend the useful life of the mold 160.
FIG. 1B is a cross-sectional view of the platen 100 taken along line B-B of FIG. 1A, in which a force has not yet been applied to the force-bearing zone 110, and the mold-bearing zone 102 is shown in a substantially flat condition. The mold 160 includes a mold half 170 and a mold half 172. The mold half 172 is shown attached to the central portion 104 of the mold-bearing zone 102. The mold half 170 is attached to another platen which is not depicted. Actuators (not depicted) have been actuated to stroke the platens that are attached to the mold halves 170, 172 so that the mold halves 170, 172 close or shut against each other to define a mold cavity 174. A molding-system nozzle 164 passes through the passageway 103 and a passageway 165 defined by the force-bearing zone 110. The nozzle 164 is positioned to communicate a molding material into the mold cavity 174.
If the platen 100 is used as a movable platen, the passageway 165 is not used. According to a variation, items 167 are tie-bar nuts that are used to attach the tie bars 166 to the peripheral corners of the force-bearing zone 110 so that the tie bars 166 may be used to transfer a clamping force and/or a mold-break force to the force-bearing zone 110. According to another variation, items 167 are clamping mechanisms that are used to apply the clamping force and/or the mold-break force to the tie bars 166 and to the force-bearing zone 110 (and items 167 may reside within the zone 110 or outside of the zone 110).
FIG. 1C is a cross-sectional view of the platen 100 taken along line B-B of FIG. 1A, in which a force 179 is shown applied to the force-bearing zone 110, and the mold-bearing zone 102 is shown maintained in a substantially flat condition under the application of the force 179. The peripheral corners of the force-bearing zone 110 receive the force 179, and then the force-transmitting structure 162 transmits a substantial portion 180 of the force 179 over to the central portion 104. However, none of the force 179 is coupled from the force-bearing zone 110 over to the peripheral portion 106 (because the portion 106 is decoupled from the zone 110). Advantageously (under this arrangement), the central portion 104 and the peripheral portion 106 do not experience warping or bending so that the life of the mold 160 may be prolonged. Disadvantageously, the force 179 inadvertently acts to bend or to warp (as indicated by arrow 182) the peripheral corners of the force-bearing zone 110 and/or the tie bars 166. The warping action associated with the portion 182 of the force 179 may cause premature and/or inadvertent wear and tear to the tie bars 166 and/or to the items 167 thus prematurely shortening their useful life. The tie-bar ears 115 may inadvertently bend if the force 179 is too large.
FIG. 1D is a perspective view of the molding-system platen 200 (hereafter referred to as the “platen” 200) which operates according to the principles of the platen 100 of FIG. 1A (but with some variations). To facilitate an understanding of the platen 200, elements that are similar to those of the platen 100 are identified by reference numerals that use a two-hundred designation rather than a one-hundred designation. For example, the mold-bearing zone of the platen 200 is labeled 202 rather than being labeled 102 (etc). The mold-bearing zone 202 no longer defines tie bar passageways. The force-bearing zone 210 defines tie-bar ears 215 (located at the four corners of the zone 210). The zone 202 now defines notches 290 that surround the tie bars at least in part. The force-transferring structure 262 is shown as a frustum-shaped body or as a frusto-conical body so that in effect the force 279 may be symmetrically applied substantially across the corners of the central portion 204. A frustum is the part of a solid (such as a cone, a pyramid, etc) between two parallel planes cutting the solid, especially the section between the base and a plane parallel to the base. The pinnacle of the frustum-shaped body is attached to the mold-bearing zone 202 and the base of the frustum-shaped body is attached to the force-bearing zone 210.
FIGS. 2A to 2D are views of molding-system platens 300, 400, 500 in accordance with U.S. Patent Application Number 2004/0208950A1. FIG. 2A is a perspective view of the molding-system platen 300 (hereafter referred to as the “platen” 300). The platen 300 is similar in some aspects to the platens 100, 200 in that the platen 300 includes a mold-bearing zone 302 and a force-bearing zone 310. The mold-bearing zone 302 includes a central portion 304 and a peripheral portion 306 that surrounds the central portion 304. The force-transferring structure 362 couples the force-bearing zone 310 to the central portion 304. However, in sharp contrast to the platens 100, 200, the platen 300 includes a plurality of ribs 311 that are placed offset from each other, that have a length and that couples the force-bearing zone 310 to the peripheral portion 306 (in sharp contrast to the platens 100, 200 in which the force-bearing zones 110, 210 are decoupled from the peripheral portion 106, 206). The ribs 311 are coupled to a force-transferring structure 362 as well. The zone 310 includes tie-bar ears at each corner of the zone 310.
A potential problem with the platen 300 is that even though the tie-bar ears 315 may be prevented from becoming deflected (that is, suppressed deflection of the tie-bar ears 315), with higher amounts of clamping force, the zone 302 may experience deflection (warping) of such a magnitude that the deflection may prevent the use of molds having larger foot prints, and may be even high enough to bend the tie bars as well. But the zone 302 could be prevented from deflecting by using a lower clamping force (unfortunately) or by increasing the mass of the zone 302 (which may inadvertently increase the cost), and if the platen 300 were used as a movable platen, then the cycle time would increase because a heavier platen has a larger inertia and therefore the heavier platen would require more time and energy to move in order to keep the cycle time—of the molding system—low.
FIG. 2B is a cross-sectional view of the platen 300 along the line BB of FIG. 2A, in which a force has not yet been applied to the force-bearing zone 310, and the mold-bearing zone 302 is flat under the state of un-applied force. The ribs 311 couple the force-bearing zone 310 to the peripheral portion 306 as well as to the force-transferring structure 362 (so that, in effect, the peripheral portion 306 is coupled to the force-bearing zone 310).
FIG. 2C is a cross-sectional view of the platen 300 taken along the line B-B of FIG. 2A, in which a force 379 is applied to the force-bearing zone 310. A portion 380 of the force 379 is transmitted from the force-bearing zone 310 via the force-transferring structure 362 to the central portion 304. However, a smaller portion 384 of the force 379 is transmitted from the force-bearing zone 310 via the ribs 311 to the portion 306, and as a result the peripheral portion 306 of the mold-bearing zone 302 becomes warped or bent while the force-bearing zone 310 remains substantially flat. Under this arrangement, in effect, the tie bars 366 and or the items 367 do not become prematurely worn down due to stresses (in sharp contrast to the tie bars 166 and the items 167 of FIG. 1B) due to the force-bearing zone 310 not bending or warping under the application of the force 379 (in sharp contrast to bending of the zone 110 of FIG. 1C). However, disadvantageously, the peripheral portion 306 experiences warping or bending due to the portion 384 of the force 379 that is transmitted from the force-bearing zone 310 to the peripheral portion 306 (in sharp contrast to the peripheral portion 106 of FIG. 1C that does not receive any force when the force 179 is applied). The arrangement of the ribs 311 may cause premature wear of the mold 360 if the footprint of the mold 360 extends into the warped peripheral portion 306. In sharp contrast, the mold 160 of FIG. 1C does not experience premature wear because the peripheral portion 106 does not experience inadvertent warping due to the applied force 179.
FIG. 2D is a perspective view of the molding-system platens 400, 500 which operate according to the principles of the platen 200 of FIG. 2A. Hereafter, the molding-system platens 400, 500 will be referred to as the “platens” 400, 500. To facilitate an understanding of the platens 400, 500 elements that are similar to those of the platen 300 are identified by reference numerals that use a four-hundred designation and five-hundred designation (respectively) rather than a three-hundred designation. For example, the mold-bearing zone of the platen 400 is labeled 402 rather than being labeled 302, while the mold-bearing zone of the platen 500 is labeled 502 rather than being labeled 302 (etc). The platen 400 is depicted as a stationary platen while the platen 500 is depicted as a movable platen.
The mold-bearing zones 402, 502 no longer define tie bar passageways. The force-bearing zones 410, 510 define tie-bar ears 415, 515 respectively. The mold-bearing zones 402, 502 now define notches 490, 590 that surround tie bars at least in part. The ribs 411, 511 are positioned symmetrically around the peripheral edge (portion) of the central portions 404, 504 respectively. The ribs 411 are aligned perpendicularly between the zones 402, 410 while the ribs 511 are aligned non-perpendicularly (angled) between the zones 502, 510. The force-transferring structures 462, 562 are shown as frustum-shaped bodies or as frusto-conical shaped bodies so that so that in effect the applied force may be symmetrically applied substantially across the corners of the central portions 404, 504. The pinnacle of the frustum-shaped body is attached to the mold-bearing zone 402, 502 and the base of the frustum-shaped body is attached to the force-bearing zone 410, 510 respectively. Each corner of the zone 410, 510 includes tie-bar ears 415, 515 respectively.
It appears the arrangements of the platens 100, 200, 300, 400 and 500 have shortcomings associated therewith.